Light-emitting devices (LEDs), such as light-emitting diodes or laser diodes, are widely used for many applications. As is well known to those skilled in the art, an LED may include a semiconductor light-emitting element having a plurality of semiconductor layers formed on a substrate. The substrate may be formed of, for example, gallium arsenide, gallium phosphide, alloys thereof, sapphire and/or silicon carbide. Continued development in LEDs has resulted in highly efficient and mechanically robust light sources that can cover the visible spectrum and beyond. These attributes, coupled with the potentially long service life of solid state devices, may enable a variety of new display applications, and may place LEDs in a position to compete with the well entrenched incandescent and fluorescent lamps.
LEDs emit light from active layers. Accordingly, light may be extracted from the opposite sides of the active layers. However, in certain situations, for example, when used for illumination, it may be preferred that the light is directed to only one side of an active layer, with the light being scattered to achieve a more uniform light distribution. Conventionally, patterned package substrates are bonded onto the LED chips to direct light to desirable directions. This, however, will increase the cost and complexity in the formation of the package substrates and the bonding process for bonding LED chips onto the package substrates. In addition, the solutions in package substrates did not help improve the light-extraction efficiency.